Funding for this research was provided by:
china scholarship council (202006230342)
project of guangxi health commission (82/03301218009D)
Article History
Received: 10 June 2021
Accepted: 17 October 2021
First Online: 22 November 2021
Declarations
:
: The data which was used in this study is secondary data. The CHARLS already obtained the ethical approval and informed consent, and was approved by research ethics committees of Peking University. In addition, the data which was used in this study was anonymised before use.
: Not applicable.
: The authors declare that they have no competing interests.